Example:

Show that cosine (5/7)π radians and cosine 128.57° are equal (to four significant digits).

Keys:

Display:

Description:

9()

 

Sets Radians mode; RAD

 

annunciator on.

 

 





5/7 in decimal format.





Cos (5/7)π.

9()



Switches to Degrees mode (no

 

annunciator).

 

 





Calculates cos 128.57°, which is

 

the same as cos (5/7)π.

Programming Note:

Equations using inverse trigonometric functions to determine an angle θ, often look something like this:

θ= arctan (y/x).

If x = 0, then y/x is undefined, resulting in the error:   .